Method for manufacturing MEMS microphone

Abstract

The invention provides a method for manufacturing a MEMS microphone, including the steps of: providing a base and preparing a first diaphragm on a first surface of the base; preparing a back plate on a surface of the first diaphragm opposite to the first surface; forming a first gap between the first diaphragm and the back plate; preparing a second diaphragm; forming a second gap between the second diaphragm and the back plate; preparing electrodes; forming a back cavity by etching the surface opposite to the first surface.

What is claimed is: 
     
       1. A method for manufacturing a MEMS microphone, comprising steps of:
 selecting a base, depositing a first oxidation layer on the first layer of the base; 
 depositing a first polycrystalline silicon layer on the surface of the first oxidation layer and patterning the first polycrystalline silicon layer to form a first vibrating diaphragm structure; 
 depositing a second oxidation layer on the surface of the first vibrating diaphragm structure, 
 depositing a material layer of back plate on the surface of the second oxidation layer, 
 patterning the material layer of back plate to form a back plate structure, wherein the back plate structure comprises multiple acoustic through holes; 
 depositing a third oxidation layer on the back plate structure, and flattening the third oxidation layer; 
 patterning the third oxidation layer and the second oxidation layer, forming a deposition hole of supporting part between the acoustic through holes, wherein the deposition hole of supporting part is exposed from the first vibrating diaphragm structure; 
 depositing the material layer of supporting part until it fills up the deposition hole of supporting part; 
 flattening the material layer of supporting part until the surface of the third oxidation layer is exposed; 
 depositing a second material layers of vibrating diaphragm, and patterning the second vibrating diaphragm material layer to form the second diaphragm structure and to form releasing holes on the second diaphragm structure corresponding to a periphery of the back plate structure; 
 preparing the extraction electrodes of the first vibrating diaphragm structure, the second vibrating diaphragm structure and the back plate structure; 
 back-etching the base to form a back cavity area corresponding to the central main body area of the back plate structure; 
 releasing the second oxide layer and the third oxide layer between the first diaphragm structure and the second diaphragm structure corresponding to the middle main body area of the back plate structure through the releasing hole, and releasing the first oxide layer above the back cavity structure through the back cavity structure. 
 
     
     
       2. The method for manufacturing the MEMS microphone as described in  claim 1 , wherein the step of the depositing of the material layer of back plate comprises a step of depositing a first nitride silicon layer, a second polycrystalline silicon layer and a second nitride silicon layer. 
     
     
       3. The method for manufacturing the MEMS microphone as described in  claim 1 , wherein the step of depositing of the extraction electrodes of the first vibrating diaphragm structure, the second vibrating diaphragm structure and the back plate structure comprises steps of:
 etching to form electrode extraction holes of the first vibrating diaphragm structure, the back plate structure and the second vibrating diaphragm structure; 
 depositing and patterning the electrode layer, form the first extraction electrode of the first vibrating diaphragm structure, the second extraction electrode of the second vibrating diaphragm structure, the third extraction electrode of the back plate structure. 
 
     
     
       4. The method for manufacturing the MEMS microphone as described in  claim 1 , wherein the step of depositing the material layer of supporting part is depositing a third nitride silicon layer on the patterned third oxidation layer. 
     
     
       5. The method for manufacturing the MEMS microphone as described in  claim 1 , wherein the forming of a back cavity structure comprises:
 thinning and etching the base from the second surface of the base. 
 
     
     
       6. The method for manufacturing the MEMS microphone as described in  claim 3 , further including a step of depositing a passivation protective layer after forming the electrode extraction hole. 
     
     
       7. The method for manufacturing the MEMS microphone as described in  claim 6 , wherein the electrode layer comprises a Cr/Au layer. 
     
     
       8. The method for manufacturing the MEMS microphone as described in  claim 1 , further comprising a step of forming a through hole through the supporting part, the first vibrating diaphragm structure, and the second vibrating diaphragm structure. 
     
     
       9. The method for manufacturing the MEMS microphone as described in  claim 1 , further including a step of forming a bump on the upper and lower surfaces of the central main body area of the back plate structure.